In general, a hinge device of this type, as described in the under-listed Patent Document 1, includes a first and a second turnable members turnably connected to each other about a turning axis, and a biasing means for biasing one of the first and second turnable members toward the other. A pair of projection parts are formed on a confronting surface with the second turnable member of the first turnable member such that they are 180 degrees away from each other in a peripheral direction. A pair of engagement recesses are formed in a confronting surface with the first turnable member of the second turnable member such that they are 180 degrees away from each other in a peripheral direction. A first cam face is formed on one side part of each engagement recess in the peripheral direction of the second turnable member and a second cam face is formed on the other side part of each engagement recess in the peripheral direction of the second turnable member. The first cam surfaces of the pair of engagement recesses are arranged 180 degrees away from each other in the peripheral direction, and the second cam faces are also arranged 180 degrees away from each other in the peripheral direction. The first cam face and the second cam face formed on the same engagement recess are arranged a predetermined angle (for example, 20 degrees) away from each other in the peripheral direction. When the pair of projection parts are brought into abutment with the first cam faces respectively, biasing force of the biasing means is converted to a turn biasing force for turning the first turnable member in one direction with respect to the second turnable member. When the pair of projection parts are brought into abutment with the second cam faces respectively, biasing force of the biasing means is converted to a turn biasing force for turning the first turnable member in the other direction with respect to the second turnable member.
In the above hinge device, since the pair of projections, two first cam faces and two second cam faces are arranged 180 degrees away from each other and the first and second cam faces are arranged a predetermined angle (for example, 20 degrees) away from each other, they may be assembled such that when the first and second turnable members are turned to predetermined positions, the pair of projections are brought into abutment with the first cam faces respectively. They may also be assembled such that the pair of projections are brought into abutment with the second cam faces respectively. If the former device is referred to as a right-hand service hinge device, the latter device can be referred to as a left-hand service hinge device.
In case a hinge device having the above-mentioned construction is used, for example, in a foldable portable telephone set as one of portable equipments, two hinge devices having difference hand services are used as one set. One of the two hinge devices turnably connects one side parts in a direction of a turning axis of adjacent end parts of a transmission section and a reception section of a portable telephone set which are one and the other of a portable equipment to each other, and the other hinge device turnably connects the other side parts of the transmission section and the reception section. The first turnable member of each hinge device is non-turnably connected to a transmission section of the portable telephone set and the second turnable member is non-turnably connected to the reception section. Owing to this arrangement, the reception section is turnably connected to the transmission section through the hinge device. The turning range of the reception section is set between a folding position where the reception section is abutted with a front surface of the transmission section and a talking position where the reception section is turned from the folding position by a predetermined angle and abutted with a predetermined part of the transmission section.
When the reception section is turned to the folding position, the pair of projection parts of the right-hand service hinge device are brought into abutment with the first cam faces respectively and the pair of projections of the left-hand service hinge device are brought into abutment with the second cam faces respectively. In that condition, the biasing force of the biasing means of each of the left-hand and right-hand service hinge devices is converted to a turn biasing force for turning the reception section in a direction (one direction) toward the folding position from the talking position. This turn biasing force keeps the reception section in the folding position where the reception section is in abutment with the front surface of the transmission section. When the reception section is turned to the talking position, the pair of projection parts of the right-hand service hinge device are brought into abutment with the second cam faces respectively and the pair of projection parts of the left-hand service hinge device are brought into abutment with the first cam faces respectively. In that condition, the biasing force of the biasing means of each of the left-hand and right-hand service devices is converted to a turn biasing force for turning the reception section in a direction (the other direction) toward the talking position from the folding position. This turn biasing force keeps the reception section in the talking position where the reception section is in abutment with a predetermined position of the transmission section.
Patent Document 1: Japanese Patent Application Laid-Open No. 2001-152728